The invention relates generally to a Time Division Duplex (TDD) radio transceiver, more particularly, to an antenna interface for a Time Division Duplex (TDD) radio transceiver.
Traditionally, a radio transceiver requires both a Low Noise Amplifier (LNA) for clear reception of a radio signal transmitted to the transceiver and a Power Amplifier (PA) for transmitting a radio signal from the transceiver over long distances.
In a Time Division Duplex (TDD) transceiver, a transmitter and a receiver are not utilized simultaneously. Typically, when the transmitter of a transceiver is on, the receiver of the transceiver is off. Likewise, when the receiver is on, the transmitter is off. For a typical TDD transceiver, to conserve power, the receiver Low Noise Amplifier (LNA) is powered down during a transmit cycle, and the transmit power amplifier (PA) is powered down during a receive cycle.
In the past, a LNA and a PA in a transceiver have been discrete components, and they have been designed independently from each other for their own optimum performance. Therefore, a LNA and a PA have been using their own set of different matching components to interface with an antenna. For example, a LNA is designed to use its own set of matching components to match its input impedance to an antenna impedance to obtain the maximum power transfer for a received signal from an antenna to a LNA. On the other hand, a PA is designed to use its own set of matching components to obtain a required output load impedance to maximize its power amplification with maximum efficiency.
Recently, as Integrated Circuit (IC) technologies improve, much effort has been made to integrate as many functional blocks as possible on a single chip to reduce its cost and size. Integration of a LNA and a PA onto a single chip often requires careful attention. For example, if a LNA and a PA use different pins, then an antenna switch is required to toggle between a LNA input and a PA output in a TDD system. However, an antenna switch is costly and will still adversely attenuate the transmit and receive signals somewhat. In addition, a control circuit must be used to switch the antenna switch between a transmit cycle and a receive cycle. Also, a Balun (Balanced/Unbalanced) circuit is used if a LNA and a PA are differential. A Balun circuit and an impedance matching circuit are used in both transmit and receive paths. Furthermore, twice as much transceiver Integrated Circuit (IC) package pins are needed to interface the transceiver with the impedance matching circuits for transmitting and receiving signals. The extra Balun circuit, the extra impedance matching circuit, and the extra transceiver IC package pins make a TDD transceiver system large in size and much more expensive.
It is with respect to these and other considerations that the present invention has been made.
In accordance with this invention, the above and other problems were solved by providing an antenna interface that allows a transceiver to be attached to an antenna/filter without the need for an antenna switch.
In one embodiment, an antenna interface for a transceiver in accordance with the principles of the present invention includes only one Balun circuit to convert a single-ended signal to/from differential signals, and only one impedance matching circuit to match an impedance at an output of the Balun circuit with an input impedance of a Low Noise Amplifier (LNA) of a receiver and to provide an output load impedance required by a Power Amplifier (PA) of a transmitter, wherein the impedance matching circuit is coupled to both the LNA and the PA. The LNA and the PA are based on CMOS technology and made within a single integrated circuit.
In one embodiment, a Time Division Duplex (TDD) transceiver system in accordance with the principles of the present invention includes an antenna for receiving and transmitting a signal; a bandpass filter to filter out noise received from the antenna; an antenna interface coupled between the bandpass filter and a transceiver; and the transceiver including a receiver Low Noise Amplifier (LNA) to amplify a signal received from the bandpass filter and a transmit Power Amplifier (PA) to amplify a signal transmitted to the bandpass filter. The antenna interface includes only one Balun circuit, coupled to the bandpass filter, to convert a single-ended signal to/from differential signals; and only one impedance matching circuit, coupled to the Balun circuit and the transceiver, to match an impedance at an output of the Balun Circuit with an input impedance of a Low Noise Amplifier (LNA) of a receiver and to provide an output load impedance required by a Power Amplifier (PA) of a transmitter, wherein the impedance matching circuit is coupled to both the LNA and the PA. The LNA and the PA are based on CMOS technology and made within a single integrated circuit.
In another embodiment, an antenna interface between an antenna and a transceiver in accordance with the principles of the present invention includes only one impedance matching circuit to match an antenna impedance with an input impedance of a Low Noise Amplifier (LNA) of a receiver and to provide an output load impedance required by a Power Amplifier (PA) of a transmitter, wherein the impedance matching circuit is coupled to both the LNA and the PA. The LNA and the PA are based on CMOS technology and made within a single integrated circuit.
In another embodiment, a Time Division Duplex (TDD) transceiver system in accordance with the principles of the present invention includes an antenna for receiving and transmitting a signal; a bandpass filter to filter out noise received from the antenna; an antenna interface coupled between the bandpass filter and a transceiver; and the transceiver including a receiver Low Noise Amplifier (LNA) to amplify a signal received from the bandpass filter and a transmit Power Amplifier (PA) to amplify a signal transmitted to the bandpass filter. The antenna interface includes only one impedance matching circuit, coupled to bandpass filter and the transceiver, to match an impedance at an output of the bandpass filter with an input impedance of a Low Noise Amplifier (LNA) of a receiver and to provide an output load impedance required by a Power Amplifier (PA) of a transmitter, wherein the impedance matching circuit is coupled to both the LNA and the PA. The LNA and the PA are based on CMOS technology and made within a single integrated circuit.